On Tue, 11 Sep 2012, Rafael J. Wysocki wrote: > Hi, > > On Tuesday, September 11, 2012, Dave Airlie wrote: > > Hi Rafael, > > > > I've been investigating runtime PM support for some use-cases on GPUs. > > > > In some laptops we have a secondary GPU (optimus) that can be powered > > up for certain 3D tasks and then turned off when finished with. Now I > > did an initial pass on supporting it without using the kernel runtime > > PM stuff, but Alan said I should take a look so here I am. > > Alan Stern or Alan Cox? :-) > > > While I've started to get a handle on things, we have a bit of an > > extra that I'm not sure we cater for. > > > > Currently we get called from the PCI layer which after we are finished > > with our runtime suspend callback, will go put the device into the > > correct state etc, however on these optimus/powerxpress laptops we > > have a separate ACPI or platform driver controlled power switch that > > we need to call once the PCI layer is finished the job. This switch > > effectively turns the power to the card completely off leaving it > > drawing no power. > > > > No we can't hit the switch from the driver callback as the PCI layer > > will get lost, so I'm wondering how you'd envisage we could plug this > > in. > > Hmm. In principle we might modify pci_pm_runtime_suspend() so that it > doesn't call pci_finish_runtime_suspend() if pci_dev->state_saved is > set. That would actually make it work in analogy with pci_pm_suspend_noirq(), > so perhaps it's not even too dangerous. This sounds more like a job for a power domain. Unless the power switch is already in the device hierarchy as a parent to the PCI device. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
